Precipitating metals from solutions.



L. D. MILLS. PEEGIPITATING METALS PROM SOLUTIONS APPLICATION FILED MAY14. 1913.

Patented J an. 5

pnrrnn erirrns i a r rl I I LOUIS DAVID MILLS, or JOHANNESBURG,nANsvAAL; son'rn AFRICA, AssreaioR To MERRILL METALLURGICAL COMPANY, ACORPORATION OF CALIFORNIA.

PRECIPITATING METALS FROM SOLUTTONS. l

essrs.

To all whom it may concern Be it known that I, LOUIS DAVID Mums, acitizen of the United States of America, residing at 4-6 CommercialExchange Building, Main street, J ohannesbin'g, in the Province oftheTransvaal, Union of South Africa, have invented certain new and use fulImprovements in Precipitating lletals from Solutions, of which thefollowing is a specification.

The present invention consists in a liltering process and apparatus fortreating solutions of precious metals .ivith mobile precipitant, vwhichmay be finely divided zinc, aluminium, charcoal or hydrocarbon ormixtures thereof; and for separating the resulting recipiate from theliquid.

The distinctive feature of the present process as compared with theknown filter ing precipitation processes consists in maintaining ahomogeneous mixture of the pregnant solution and mobile precipitant atthe surface of the filtering medium, so that as the solution is passedthrough said medium the precipitant and precipitate are deposited on thefilter as a tomogelneous and uniformly permeable cak Siuch homogeneityof the mixture is usually maintained continuously circulatitn" it.

The invention may be carried into effect by means of the apparatus shownin the accompauvin drawin which is a. vertical.

section.

1 indicates a 'at or other receptacle adapted to hold liquid andcontaining a number of filter leaves 2. The latter are preferablydisposed vertically as shown in order to facilitate the circulation "ofthe solution and precipitant as described; hereafter. Suitable-meanssuch as the connections 3, pump 4 and delivery pipe 5 therefrom areprovided for exhausting the interior of the filter lea es or otherwiseproducing the necessary difference of pressure be tween their interiorand exterior surfaces, and for disposing 0f the liquid thereby caused topass into them.

In th arrangement shown, the fluid mixture of solution and precipitantis distributed below the normal surface of the liquid in the receptacle,but above the filter leaves, by means of a number of hol ow arms (3furnished With numerous outlets 7 Specification of'Letters Patent.

which are so -arranged as-to distribute the r ,vture uniformly. a'blyrevolved slowly, for which purpose Patented Jan. 5, 191-5. Applicationfiled May 14., 1913. Serial No. 767,512. i

The arms are" prefer-.

they are mounted on a spindle 8 which also carries a hopper 0 from whichthe liquid and precipitant are fed to the arms.

10 'IS a pipe connection from the bottom .00. of the vat, '11 av pumpand 19. a delivery pipe therefrom by which the mixture drawn from thebottom of the receptacle, is returned into the hopper 9 forredistribution; Fresh precipitant is delivered to the hopper 9 asrequired by the device 13.

-1l IS a source of pregnant solution having a delivery pi e Lrand avalve 16 controlled" by a float 17 whereby fresh solution is added tosupply the place of that drawn 'oll' during operation and therebymaintain the liquid in the vat at'constant level. Pipes 12 and '15 dipbeneath the surface 18 of the liquid' an hopper 9 to preventdetrimei'ital-agita Lion of the solution and oxidation of theprecipitant suspended in it.

Provision is made for thorougl'ily removing the solid matter which tendsto collect at the bottom of the receptacle and passing the same into thecirculatory system to be re-mixed with the solution. For this purpose inthe ap 'iaratus illustrated, the bottom 19 of the receptacle is slightlysloped toward a central outlet 20 from which the circulating pump 11draws its supply. A. number of mo ing plows or scrapers 21 which may becarried bv arms 22 project ng from t'lu;: rotating spindle 8 arearranged to pass the settled material to said outlet 20. device of thischaracter enables the amount of precipitant not deposited on the ,filterleaves and not in active circulation precipitant, together with suchquantities of precipitate as may have already been formed by theinteraction of the precipitant with the liquid in which it is suspended.The fine granular structure of the cake causes every particle of thesolution which continues to pass through it to be brought into veryintimate contact with the precipitant whereby a very completeimpoverishment of the solution is brought about; and as the impoverishedliquid is at onceby passing through the filter medium-removed fromfurther contact with the precipitate, re-solution of the latter isobviated. As is well known, a filter cake thus formed by immersing thefilter leaves in a homogeneous mixture of liquid and solid matter-tendsautomatically to attain and maintain homogeneity of structure anduniform permeability throughout; so that, in the present case, the wholeof the solution is equally subjected to the action of precipitant. Asmore-and more solution passes through the filter, so is the deposit ofprecipitant thereon replenished and the precipitating activity of thecake is maintained. When it is desired to recover the precipitate, thesupply of fresh solution and precipitant is shut off and as much of theremaining liquid as is possible is drawn oil through the filter leavesby pump 4. The pump 4 may then be stopped and the precipitate sluicedoff into the bottom of the vat from which it is removed by thecirculating pump and passed by its branch outlet 23 to such furthertreatment in a filter press or otherwise as may be expedient.

What I claim and desire to secure by Letters Patent is l. The process ofprecipitating metals from their solutions which consists in maintaininga homogeneous mixture of said solutions and a mobile precipitant at thesurface of a filter medium, withdrawing solution through said mediumwhereby the solid matter suspended therein is deposited as a homogeneousand uniformly permeable layer on said medium, and circulating the excessmixture adjacent to said filtering medium.

2. The process of precipitating metals from their solutions whichconsists in maintaining a homogeneous mixture of said solutions and amobile precipitant at the surface of a filter medium, withdrawingsolution through said medium whereby the solid matter suspended thereinis deposited as a homogeneous and uniformly permeable layer on saidmedium, collecting the heavier settled particles of the participant andprecipitate and circulating the mixture containing said heavierparticles adjacent to said filter-medium.

In testimony whereof I afiix my signature in the presence of twowitnesses.

VVEsLuY E. JOHN, J. WARREN VENNING.

